webadmin: GuideMe cluster does not pass OverrideFirewall

- Fixed class cast exception in onAddHost()
- Added passing OverrideFirewall in onAddHost()

Change-Id: I8b9c2c57ffc2be7fa5a7e57675b4c82d5c789ae6
Bug-Url: https://bugzilla.redhat.com/show_bug.cgi?id=998938
Signed-off-by: Alexander Wels <awels@redhat.com>